Optical recording media which have recently been developed are advantageous in that they have a recording or storing capacity much larger than that of conventional magnetic recording media. This is due to a feature of the optical recording media that it can record or store data at a high density within a small area. To read the data recorded at a high density in a small area or write data into a small area at a high density, recording/writing elements must accurately track the data recorded on the media or data track in which the data is to be recorded.
For this purpose, heretofore, there has been known a system in which a data track is set centrally in an elongated data recording region which is provided between each two adjacent tracking lines provided at predetermined intervals on a optical recording medium.
According to the system, two tracking lines, between which the recording region is provided, are used for effecting the reading/writing operation, i.e., they are traced or followed to read or write the data on the data track in the data recording region. Thus, highly accurate reading/writing operation can be assured.
In such a system, a single data track is provided in one band of data recording region, so that the data tracks and the tracking lines are arranged alternatingly in a data storage section of the optical recording medium. Due to this structural feature, this system has such a disadvantage that the data recording capacity in a limited size of the medium is prevented from being increased due to the spaces occupied by the tracking lines provided for every data track.
To solve this problem, it can be considered to reduce the distance between the tracking lines. In effect, however, there is a limit in the shortening of the intervals between the tracking lines, for a technical reason such as a technical difficulty of forming minute patterns of the tracking lines in the manufacturing process of the medium.
It is therefore an object of the present invention to provide an optical recording medium which is capable of setting a plurality of data tracks within a data recording region, allowing high-density data recording, thereby to remarkably increase a recording capacity.
It is another object of the present invention to provide a tracking system adapted for an optical recording medium in which a plurality of data tracks are set within one data recording region, which system is capable of effectively reading or writing data from or into each of the data tracks.